Attention Deficit Disorder with Hyperactivity (ADDH) is a life-long disability affecting approximately 4% of school age children. To understand the pathophysiology of this disorder and to develop new treatments, a therapeutic trial of the amino acid, d-phenylalanine, was completed over the past nine months. Eleven ADDH boys participated in a placebo controlled double blind evaluation of phenylalanine (10/mg/kg/day) and placebo. Behavioral data and biochemicl measures in urine and plasma are being analyzed at present and results are forthcoming. In an attempt to localize abnormal patterns of cerebral glucose metabolism and cerebral flow in adults with Attention Deficit Disorder (ADD) Residual Type, fathers of diagnosed hyperactive children are being studied using the 2-deoxyfluoroglucose method of Positron Emission Tomography (PET). To date, four patients have been scanned. Because of reports that the spinal fluid (CSF) 5HIAA, a serotonin metabolite, may be low in severely impulsive or aggressive adults, a study has been initiated to compare spinal fluid catecholamine and indoleamine metabolites in severely aggressive, conduct disordered children with and without ADD to children with other neurological problems. Peripheral measures of catecholamines will also be obtained.